Consistent population declines but idiosyncratic range shifts in Alpine orchids under global change

Abstract

Mountains are plant biodiversity hotspots considered particularly vulnerable to multiple environmental changes. Here, we quantify population changes and range-shift dynamics along elevational gradients over the last three decades for c. two-thirds of the orchid species of the European Alps. Local extinctions were more likely for small populations, after habitat alteration, and predominated at the rear edge of species’ ranges. Except for the most thermophilic species and wetland specialists, population density decreased over time. Declines were more pronounced for rear-edge populations, possibly due to multiple pressures such as climate warming, habitat alteration, and mismatched ecological interactions. Besides these demographic trends, different species exhibited idiosyncratic range shifts with more than 50% of the species lagging behind climate warming. Our study highlights the importance of long-term monitoring of populations and range distributions at fine spatial resolution to be able to fully understand the consequences of global change for orchids.

Butterfly communities track climatic variation over space but not time in the Iberian Peninsula

“…Hence, it is likely that species would have been able, if needed, to shift their distributions locally within 10 km grid squares to maintain associations with favourable climatic conditions (Roth et al ., 2014; Colom et al ., 2020). Local range shifts could occur via movements to higher elevations (Wilson et al ., 2007; Geppert et al ., 2020; Marshall et al ., 2020), or to cooler microclimates on north‐facing slopes or in narrow valleys (Scherrer & Körner, 2011), which could provide locally cooler or moister conditions. Butterflies can also respond in situ to climatic variability through changes to behaviours such as egg‐site selection (Bennett et al ., 2015), basking (Barton et al ., 2014) and aestivation (García‐Barros, 1988), and through plasticity in physiology and morphology (e.g., de Jong et al ., 2010; Gibbs et al ., 2011).…”

Combining current knowledge of Cypripedium calceolus with a new analysis of genetic variation in Italian populations to provide guidelines for conservation actions

“…As the Apennine populations of C. calceolus are the southernmost in Europe (but note that a disjunct population was recently discovered in Algeria; Nemer, Rebbas, & Krouchi, 2019), they may be considered vulnerable "edge populations" (but see García et al, 2010). This hypothesis is supported by the recent findings of elevation range shift towards higher elevations for C. calceolus in the Alpine range (Geppert et al, 2020;Perazza & Chini, 2020). However, species distribution/ecological niche modeling includes the Apennines in the area/niche of current and future suitability for the species, although possibly subject to range contraction (Gargiulo et al, 2019;Kolanowska & Jakubska-Busse, 2020).…”

“…We recognize that further cost reductions associated with high-throughput methods may allow questions about adaptive variation, in addition to selectively neutral variation (Flanagan, Forester, Latch, Aitken, & Hoban, 2018;Funk, McKay, Hohenlohe, & Allendorf, 2012), to be addressed, but some populations of C. calceolus require immediate action, and we cannot afford to wait for such cost reductions. Unfortunately, there is also uncertainty associated with the future implications of climate change (Geppert et al, 2020;Kramer & Havens, 2009), especially in edge populations, where conditions may become unsuitable for the species. While such uncertainty should be considered in refining strategies (Rusconi, 2017), it should not discourage their implementation in the first place, as populations of C. calceolus have primarily disappeared because of human actions, and therefore it is a human responsibility to reverse the damage.…”

A quantitative review of abundance-based species distribution models

“…Mismatches arise from different ecological controls of abundance and occurrence, such as different demographic rates controlling each to different extents (McGill 2012, Johnston et al 2015, Acevedo et al 2017, Dallas and Santini 2020, Schulz et al 2020, Yancovitch et al 2020, Bohner and Diez 2020). Understanding such mismatches offers an important avenue for better understanding range and abundance shifts under climate change (Geppert et al 2020) and potentially guiding spatial management and conservation. For example, a focus on occurrence can miss critical patches of high abundance driven by a few isolated factors (Johnston et al 2015, Suggitt et al 2018).…”